The invention relates to a magnetic stirring apparatus. The invention further relates to an agitating device activated by the magnetic stirring apparatus.
Bar magnets are known which are used to stir liquids by adding the bar magnet to a container containing liquid and setting the container on a rotating magnetic field so that the bar magnet is set into rotation.
It is disadvantageous with such bar magnets that they rest on the bottom of the container and thus only generate a limited stirring effect. The frictional forces occurring between the bar magnet and the bottom can moreover effect abrasion or destroy parts, such as living cells, contained in the liquid.
It is an object of the present invention to propose a more advantageous magnetic stirring apparatus and a more advantageous agitating device.
The object is satisfied in particular by a magnetic stirring apparatus comprising an agitator, a permanent magnet and a float body, which are connected to one another.
An important aspect of the invention comprises the magnetic stirring apparatus being formed such that the agitator is arranged spaced from the bottom of the container so that the agitator no longer slidingly rotates on the bottom during stirring.
In a preferred embodiment, the magnetic stirring apparatus is formed in an elongate, essentially bar-like manner, with the agitator being arranged in the region of the first end section and a float body being arranged in the region of the second end section. In a particularly advantageous embodiment, the end of the first end section is formed as a tip. This magnetic stirring apparatus is put into a container containing liquid, with the magnetic stirring apparatus being held in an essentially vertically extending orientation and being stabilized against tilting by the buoyancy forces acting on the float body. The float body thus effects a hydrodynamic stabilization of the magnetic stirring apparatus against tilting and thus stabilizes the magnetic stirring apparatus with respect to two degrees of freedom.
A device is arranged beneath the bottom of the container which allows a magnetic rotating field to be generated. This device is formed in a preferred embodiment as a magnetic coupling comprising a rotating permanent magnet. This permanent magnet acts on the permanent magnets arranged in the agitator. The position of the agitator and thus the position of the magnetic stirring apparatus is determined with respect to three degrees of freedom, namely in the x and y directions and with respect to the rotation, by the magnetic coupling formed in this way. This is only stabilized with respect to a downward movement in the vertical direction, that is, in the direction of extension of the magnetic stirring apparatus, by the tip which forms a toe bearing together with the bottom of the container. Together with the downward acting magnetic force of the magnetic coupling, the vertical degree of freedom (z direction) is also stabilized.
The magnetic stirring apparatus is thus stabilized with respect to six degrees of freedom. The known bar magnet initially mentioned is only stabilized with respect to four degrees of freedom, namely in the x and y directions, with respect to rotation, since it is on the bottom of the container, and with respect to a downward movement. The magnetic stirring apparatus in accordance with the invention thus has the advantage that it is stabilized with respect to more degrees of freedom, which allows the agitator to be arranged spaced from the bottom of the container.
In a further advantageous embodiment, the magnetic stirring apparatus is arranged in a floating manner in the liquid of the container, with the magnetic stirring apparatus being drivable via a magnetic field arranged outside the container. The rotating magnetic field required for the drive can be generated with the aid of electromagnetic coils or with pivoted magnets, in particular with pivoted permanent magnets which form a magnetic coupling with the magnetic stirring apparatus. Moreover, the position of the magnetic stirring apparatus is influenced in an advantageous embodiment using the permanent magnets by these permanent magnets forming part of a passive magnetic bearing. The one part of the passive magnetic bearing is arranged outside the container and exerts a stabilizing effect on the position of the magnetic stirring apparatus located inside the container.
The object is further satisfied with an agitator comprising a magnetic stirring apparatus having one or more permanent magnets and a float body and comprising a magnetic drive device, with the drive device and the permanent magnets of the magnetic stirring apparatus being arranged and formed in a mutually matched manner such that they form a magnetic coupling.
The invention is described in the following by way of several embodiments.